IBM's corporate blog strategy is the topic of this excellent article, well worth the read for any company that's remotely open to innovative uses of technology.
IBM started a major initiative last May with three approaches, accomplishing three goals: corporate sponsored blogs on their products (thought leadership), internal employee blogs (internal communication), and a policy with encourages employees to blog publicly on any topic as long as they follow some common-sense guidelines (learning & growth). The reason why is summed up here:
IBM, like many companies, set up an internal blog capability to get comfortable with the new technology. The postings are evolving over time, from individual postings on personal topics to a company-wide collaboration tool.
Big Blue bit by the blogging bug By JULIE MORAN ALTERIO (THE JOURNAL NEWS, January 9, 2006)